1. Field of the Invention
The present invention relates generally to powered cutting and trimming devices, and more specifically to a cutting head for a string or filament type grass cutting or trimming machine. The present cutting head provides positive means for locking the cutting elements at any one of a series of specific heights above the bottom of the central core of the head, and thus above the ground surface against which the head bears during cutting and trimming operations. Additional features, such as means for removably securing a series of cutting strings or filaments in the head, are also disclosed.
2. Description of the Related Art
The principle of a rapidly spinning flexible filament for use in cutting grass and other vegetation, has been expanded to include its use in wheeled (ground supported) mowers and trimming machines, as well as hand held grass cutting and trimming machines. There are essentially two problems with such devices: (1) It is difficult to hold or maintain an accurate and consistent cutting height, and (2) the string filament cutting elements are relatively soft and fragile in comparison to rigid steel cutting blades, and require frequent replacement.
While the string replacement problem has been responded to in a number of different ways, they have generally not been totally satisfactory. The easiest means of string or line replacement, by means of a so-called "bump feed" cutting head, is not adaptable to specific height adjustment due to its configuration. Most devices of the prior art have been directed away from any provision for positive, accurate height adjustment of the cutting head, in order to provide for ease of line replacement when the cutting line becomes worn or broken.
Accordingly, a need will be seen for a string trimmer type cutting head which provides positive adjustment for cutting height, and which also provides relative ease of adjustment of the cutting string or line as well. The present invention responds to both of these requirements in a single device, which is adaptable to virtually any type of powered string trimmer machinery.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 4,062,115 issued on Dec. 13, 1977 to William R. Lee, titled "Rotary Garden Cutter," describes a string trimmer type cutting head in which a plurality of separate strings are held in place by sandwiching them in a circumferential space between an inner core and an outer sleeve, with the ends of the lines passing outwardly through holes in the sleeve. The inner core is unscrewed relative to the outer sleeve to loosen the lines for replacement, and must be removed completely in order to access the interior of the sleeve to guide the replacement line through the sleeve holes. Lee does not provide any means of adjusting the cutting height of his cutting head. In contrast, the present cutting head strings are held in place by a series of independently secured peripheral clamps, providing for the replacement of a single string or line at a time, if required. The string or line attachment clamps need only be loosened slightly, to permit complete replacement of the cutting filaments. The present cutting head also includes cutting height adjusting means.
U.S. Pat. No. 4,726,176 issued on Feb. 23, 1988 to David L. McGrew, titled "Rotary Mower Cutter Means," describes a cutting head having a series of radial trimming string passages formed therein, terminating in a central recess. The cutting strings are passed through adjacent passages, with the central portions of all of the strings being clamped in place in the central recess by a single large washer or plate. As all of the cutting strings or elements are secured by a single threaded fastener, they cannot be loosened independently to provide for the replacement of a single element at a time. McGrew does not disclose any means of adjusting the cutting height for his cutting head, as provided by the present invention.
U.S. Pat. No. 4,756,146 issued on Jul. 12, 1988 to Russell V. Rouse, titled "String Trimmer Head And Method," describes a head formed of two mirror image stamped discs, with each disc having a series of semicircular trimmer string channels formed therein. The two discs are permanently assembled with the channels in registry to form a series of closed line passages. The trimmer string or line is held in place by routing it through one arcuate passage, along a peripheral groove between the first and a second passage, and then through the second passage. No mechanical clamping means is used to secure the trimmer line within the Rouse cutting head, as opposed to the present trimmer head with its mechanical clamps for securing the line segments. Moreover, Rouse does not provide any form of height adjustment for his trimmer head, as provided in the present string trimmer head invention.
U.S. Pat. No. 4,819,416 issued on Apr. 11, 1989 to Dallas W. Jones, titled "Rotary Cutting Member For Use With Lawnmowers And The Like," describes a cutting head having a series of line holding elements, with the line being looped through each of the elements. The line is held in place by the relatively tight bend formed in the line due to the close proximity of the adjacent line passages. While each line may be serviced independently of the others, no mechanical clamping means is provided to secure the lines positively in place, as provided in the present cutting head. Moreover, Jones does not provide any means of adjusting the cutting height for his trimmer head.
U.S. Pat. No. 4,873,819 issued on Oct. 17, 1989 to Charles C. Shivers et al., titled "Grass Trimmer," describes a "unicycle" type cutting machine, in which a single wheel is positioned concentrically beneath the cutting head. The only means of height adjustment is to tilt the entire machine in one direction or another, which means is well known in hand held grass trimmers and the like. No means of keeping the cutting head level, while still providing height adjustment for the cutting elements, is disclosed in the Shivers et al. U.S. Patent. Moreover, Shivers et al. utilize a pair of rigid cutting elements which are bolted to the periphery of the cutting head, unlike the multiple flexible string or filament cutting elements of the present trimmer head.
U.S. Pat. No. 4,905,465 issued on Mar. 6, 1990 to Dallas W. Jones et al., titled "Rotary Cutting Member For Use With Lawn Mowers And The Like," describes a ring having a plurality of vertically stepped holes in the side thereof. The stepped holes provide for the installation of a plurality of cutting strings or lines therethrough, with the lines being doubled over inside the ring for retention of each line. The stepped holes provide for each line to be installed at a different height to provide a series of different cutting heights, rather than for adjustment of a single plane cutting height, as provided by the present cutting head. In the event that the user wishes to adjust the cutting height of the Jones et al. device, each line must be removed from its installed point in the ring and replaced at the new location for the new height desired, whereas the cutting heights of all of the cutting elements of the present cutting head are adjusted simultaneously by means of only a few bolts. It is also noted that the installation of the trimmer lines at different heights in the Jones et al. cutting head, results in opposite cutting lines not being precisely opposite one another, thus creating imbalance in the device. The present cutting head does not have this problem.
U.S. Pat. No. 4,962,630 issued on Oct. 16, 1990 to Dallas W. Jones, titled "Rotary Cutting Member With Flexible Filaments For Use With Lawnmowers And The Like," describes a device which is essentially a combination of the '416 and '465 U.S. Patents issued to the same inventor, and discussed further above. A plurality of arms is provided, with each arm having means for holding a doubled flexible cutting line element therein. The two holes provided for each line are at different heights to provide two different cutting heights simultaneously, but no adjustment is provided; each pair of holes in each arm is the same height. As in the other Jones U.S. Patents discussed above, no positive mechanical locking means is provided for securing the cutting elements, nor is any height adjustment provided for the cutting head, as provided by the present cutting head invention.
U.S. Pat. No. 5,023,998 issued on Jun. 18, 1991 to Andrew M. Masciarella et al., titled "Filament Holder For A Rotating Filament Vegetation Cutter," describes a string trimmer head in which two cutting lines extend from one side of the head to the other, crossing one another as they pass the central driveshaft of the device. The two lines describe a sinusoidal path as they pass through various gripping elements to hold them in place. No positive mechanical clamping means is provided for securing the lines in the Masciarella et al. cutting head, nor is any means provided for adjusting the height of the Masciarella et al. cutting head, as provided by the present filament cutting head invention.
U.S. Pat. No. 5,048,278 issued on Sep. 17, 1991 to Dallas W. Jones et al., titled "Rotary Cutting Member For Use With Lawn Mowers And The Like," describes a flexible cutting line trimmer head somewhat resembling that of the '465 U.S. Patent to the same inventor, discussed further above. The device of the '278 U.S. Patent comprises a generally disc shaped cutting head having a plurality of generally radially disposed trimmer line passages. The trimmer lines are passed through adjoining passages to form a generally U-shaped path in the head. The outlets of each of the passages are at different heights relative to one another, to provide a plurality of different cutting heights. However, no means is provided for adjusting the cutting height of the device, nor is any positive mechanical means provided for clamping the cutting filaments in place, as provided in the present cutting head.
U.S. Pat. No. 5,197,264 issued on Mar. 30, 1993 to Paul Lacey, titled "Universal Filament Trimmer Head," describes a string trimmer head in which each of a plurality of cutting lines is double looped through a series of four holes in the periphery of the device, to hold the lines in place. No positive clamping means is provided by Lacey for holding the lines in place, as provided in the present line trimmer head. In addition, Lacey does not provide any means of adjusting the cutting height for his trimmer head, which feature is an important part of the present string trimmer head invention.
U.S. Pat. No. 5,713,191 issued on Feb. 3, 1998 to Michael Welton, titled "Monofilament Line Based Cutter Assembly," describes a line trimmer head comprising a flat disc with a plurality of pairs of holes adjacent its edge. The cutting string or line is looped through adjacent holes with the friction of the bends in the line passing through the holes, holding the line in place. This is similar to the line holding means disclosed in the '416, '465, '630, and '264 U.S. Patents discussed further above; no positive clamping means is provided for positively securing the line in place on the head in any of the above patents. Moreover, Welton does not provide any means for adjusting the height of the cutting head or disc, as provided by the present invention.
Finally, U.S. Pat. No. 5,862,655 issued on Jan. 26, 1999 to Rolando Altamirano et al., titled "Adjustable Mowing And Trimming Apparatus," describes a wheeled line trimmer machine in which the cutting head comprises a spindle head with a cutting element having a split ring configuration, adjustably secured thereto. The cutting element is secured to the spindle head by a pinch bolt. While this arrangement provides infinitesimal adjustment of the cutting height, the cutting element is subject to slippage on the spindle head, due to the lack of positive locking of the cutting element to one of a series of specific locations on the spindle head. In practice, the infinitesimal adjustment is unnecessary in any event, with the height adjustment to the nearest inch, or perhaps half inch, being more than sufficient in the real world of slightly uneven terrain, even in a well maintained lawn. It is also noted that the requirement for a pinch bolt through one side of the cutting disc element, precludes any provision for the attachment of trimmer line to that point of the disc, thus reducing the number of trimming line elements which may be deployed from the disc. The pinch bolt attachment, with its relatively heavy bolt disposed to one side of the disc, results in an unbalanced condition for the disc, setting up undesirable vibrations during the operation of the machine, which result in more rapid wear of the machine and fatigue for the operator of the machine and which likely lead to the difficulty in locking the cutting disc in place to prevent movement thereof on the spindle head.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.